Is there something like Annotation Inheritance in java?

java

annotation-inheritance

spring-annotations

annotation-magic

byAlex Kataev·Feb 25, 2025

Java's @Inherited meta-annotation allows subclassing types to inherit a superclass's annotations—but only those at the class level, not for methods or fields. @Inherited is marked on your custom annotation. This is a compiler hint; runtime behavior may need explicit handling. An illustration:

@Inherited
@Retention(RetentionPolicy.RUNTIME)
public @interface Inheritable {} // Parent of all annotations

@Inheritable // Soaking up the inheritance goodness
public class Base {}

public class Derived extends Base {} // Covertly getting the Inheritable perks

// Retrieval
boolean isInherited = Derived.class.isAnnotationPresent(Inheritable.class); // Not a DNA test but works

The Derived class silently inherits the @Inheritable annotation, allowing annotation-based configuration or logic to be generically applied.

Delving into annotation inheritance mechanics

If you're looking to add more muscle to your annotation's inheritance capability, there are a few power tools you can consider. Libraries like Spring leverage base annotations to allow annotations to act like they have a family tree. For instance, Spring's @Transactional annotation can be composed into custom annotations:

@Transactional
public @interface MyTransactional {} // Its all in the family

When AnnotationUtils.findAnnotation holds the treasure map leading to the nested annotations.

For controlling the realm (type, method, or field) an annotation can be applied to, the @Target annotation serves as your scepter. Use it to define your kingdom's boundaries.

Extending annotations with custom libraries

When in-house Java options fall short, third-party libraries step in. A library like annotation-magic offers the @Extends and @AliasFor annotations, allowing to create and alias attributes, thus offering a magic wand for annotation inheritance:

@Extends(MyAnnotation.class)
public @interface AdvancedAnnotation {
    @AliasFor(annotation = MyAnnotation.class, attribute = "name")
    String advancedName() default "default";
} // Don't we all wish we could `extend` in everyday life?

Your annotations now have extra features, like a deluxe edition DVD.

Everyday use and annotation patterns

Let me drop some practical knowledge on you. isPresent and annotationType() are the Batman and Robin of the Annotation interface. You can check for a specific annotation's presence and also fetch its actual type. Diversity, remember? (Batman crashes through windows, Robin uses doors).

Case study: Beyond `@Inherited`

While @Inherited adds some superhero abilities to your annotations, it has its kryptonite: it's confined to class-level annotations. For method or field level, you'd need to suit up (aka manual labor). You can scan for method annotations using loops and consider nested types in your checks.

Checking out Spring's base annotations offers a look at solving practical annotation inheritance concerns. You don't need to invent a new bicycle if you can learn to ride the existing one well.

Designing Annotations: A gentle reminder

Great-power-great-responsibility cliche aside, designing effective annotations requires having in-depth knowledge about what you're doing. R&D should be your two best friends. Dig through documentation, code examples, and all the treasure you can find.

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